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Drink less for a healthier heart

11 July 2014

A reduction in alcohol
consumption, even for light-to-moderate drinkers, could be linked to improved
cardiovascular health, including a reduced risk of coronary heart disease,
lower body mass index and blood pressure, according to new research published in the BMJ.

These latest findings
challenge the results of previous observational studies which found that the
consumption of light-to-moderate amounts of alcohol (12-25 units per week) may
have a protective effect on cardiovascular health.

The research, led by UCL, the London School of Hygiene & Tropical Medicine and the University of Pennsylvania, looked at evidence from over 50 studies into
the drinking habits and cardiovascular health of over 260,000 people. They found
that individuals who carry a genetic variant which tends to lower their alcohol
consumption have, on average, a more favourable cardiovascular profile. The
authors say this suggests that a reduction in alcohol consumption, even for
light-to-moderate drinkers, is beneficial for cardiovascular health.

Specifically, the researchers
found that these individuals had on average a 10% lower risk of having coronary
heart disease, lower blood pressure and a lower Body Mass Index (BMI).

Senior author Professor Juan P. Casas of the UCL Institute of Cardiovascular Science and the London School of Hygiene & Tropical
Medicine, said: “While the damaging effects of heavy alcohol consumption on the
heart are well-established, for the last few decades we’ve often heard reports
of the potential health benefits of light-to-moderate drinking. However, we now
have evidence that some of these studies suffer from limitations that may
affect the validity of their findings. In our study, we saw a link between a
reduced consumption of alcohol and improved cardiovascular health, regardless
of whether the individual was a light, moderate or heavy drinker. Assuming the
association is causal, it appears that even if you’re a light drinker, reducing
your alcohol consumption could be beneficial for your heart.”

In this study, the
researchers used a gene that serves as an indicator of alcohol consumption.
Individuals that carry a genetic variant of the ‘alcohol dehydrogenase 1B’ gene
are known to breakdown alcohol at a different pace. This causes unpleasant
symptoms including nausea and facial flushing, and has been found to lead to
lower levels of alcohol consumption in the long term. By using this genetic
variant as an indicator of lower alcohol consumption, they were able to find
associations between these individuals and improved cardiovascular health.

Studies into the long-term
health effects of alcohol can be challenging, due to the difficulty of setting
up randomised control trials involving many individuals who will maintain the
same alcohol consumption levels over an extended period of time. The authors
say that their study’s genetic approach parallels the principles of a
randomised control trial and therefore makes it less prone to some of the
limitations of previous observational studies. These limitations are partly due
to bias from the effects of other good health behaviours associated with a
lifestyle of low-to-moderate alcohol consumption. This may explain why a
protective effect has been observed in past studies, but does not mean that
alcohol itself is protective.

Previous observational
studies are also limited by the issue of distinguishing between self-reported
non-drinkers, who may include those who have never consumed alcohol, and those
who consumed alcohol in the past but have since stopped as a result of
ill-health. Issues like these make it difficult for observational studies to
assess the health effects of long-term alcohol consumption levels.

The current study’s results
strongly suggest that reduction of alcohol consumption is beneficial for
cardiovascular health, and is closer to establishing causality than
observational studies, however further replication of similar genetic studies
using large-scale prospective studies, such as the UK Biobank, will be needed.

The study was funded by the
British Heart Foundation and the Medical Research Council.

Dr Shannon Amoils, Senior
Research Advisor at the British Heart Foundation, said: “Studies into alcohol
consumption are fraught with difficulty in part because they rely on people
giving accurate accounts of their drinking habits. Here the researchers used a
clever study design to get round this problem by including people who had a
gene that predisposes them to drink less. The results reinforce the view that
small to moderate amounts of alcohol may not be healthy for the heart although
the study would need to be repeated in a larger group of people for definitive
results. Whilst the heart health effects of light to moderate alcohol
consumption are still unclear, what is clear is that drinking more than the recommended
limits of alcohol can have a harmful effect on the heart.”

The study was an
international collaboration that included 155 investigators from the UK,
continental Europe, North America, and Australasia.